IMMUNOSUPPRESSION - PRE-CLINICAL AGENTS

J. Grahammer¹, C. Krapf², T. Hickethier², B. Zelger³, C. Seger⁴, H. Pfisterer⁴, G. Brandacher⁵, R. Öllinger⁶, W.P.A. Lee⁷, R. Margreiter⁶, J. Pratschke⁶, H. Glossmann⁸, S. Schneeberger⁹, T. Hautz^10
1Dept. Of Visceral, Transplant And Thoracic Surgery, Center of Operative Medicine, Innsbruck Medical University, Innsbruck/AUSTRIA, ², Center of Operative Medicine, Medical University Innsbruck, Innsbruck/AUSTRIA, ³, Dept. of Pathology, Innsbruck Medical University, Innsbruck/AUSTRIA, ⁴, Central Institute of Medicinal and Chemical Laboratory Diagnostics, University Hospital, Innsbruck/AUSTRIA, ⁵, enter of Operative Medicine, Innsbruck Medical University, Innsbruck/AUSTRIA, ⁶Visceral, Transplant And Thoracic Surgery, Medical University Innsbruck, Innsbruck/AUSTRIA, ⁷Division Of Plastic And Reconstructive Surgery, UPMC, Pittsburgh/UNITED STATES OF AMERICA, ⁸, Institute of Biochemical Pharmacology, Innsbruck Medical University, Innsbruck/AUSTRIA, ⁹Transplant Surgery, University Hospital, Innsbruck/AUSTRIA, ¹⁰, Center of Operative Medicine, Innsbruck Medical University, Innsbruck/AUSTRIA

Body: Background: Skin rejection in reconstructive transplantation is primarily effected by a T-lymphocyte driven immune response towards the epidermis. Kv1.3 potassium channels on lymphocytes are critically involved in T cell activation. The effect of correolide C, a blocker of Kv1.3 was investigated in a rat limb transplant model. Methods: After orthotopic rat hind limb allotransplantation (BN-LEW) animals received correolide C either i.p. (5mg/kg/day) or as intra-graft treatment (3mg/kg twice/week s.c. into the limb) in combination with tacrolimus, given i.p. for 30 days (0.3mg/kg/day) or 50 days (0.3mg/kg/day0-30 and 0.1mg/kg/day31-50). Untreated animals, placebo treated animals and animals receiving tacrolimus alone served as controls. Rejection was assessed by daily inspection and H&E-histology of skin biopsies. Grade III rejection was defined as end-point. Tacrolimus 24h-trough blood levels were measured regularly after pod 30. WBC and RBC counts were recorded in native and correolide C (i.p. only) treated animals. Results: Untreated and placebo treated controls rejected at day 8.83+/-0.98 and 9.00+/-2.83 (p=0.894). When given i.p., correolide C monotherapy resulted in slight but significant prolongation of allograft survival (10.50+/-1.38, p=0.037). Histology showed only a mild lymphocytic infiltrate and single vacuolized keratinocytes in the epidermis on pod 10 in 4/6 correolide C treated animals. RBC counts were decreased, whereas WBC counts were increased in correolide treated animals on pod 14, compared to native animals (RBC: 4.80+/-1.07 vs. 8.44+/-0.58, p=0.00023; WBC: 30.74+/-1.40 vs. 13.20+/-3.27, p=0.000097). After weaning tacrolimus on pod 30, limbs were rejected by pod 40.00+/-1.00 (grade III), and histology revealed necrosis of the epidermis. Additional treatment with local correolide C resulted in an insignificant prolongation of graft survival (pod 43.00+/-3.74; p=0.24). 2/5 animals showed intact skin with a mild dermal infiltrate until day 45. Weaning tarcolimus on pod 50 resulted in rejection of the limb by day 55.00+/-0.00 regardless of correolide therapy. Tacrolimus mean blood levels were 2.97+/-0.98 ng/ml when tacrolimus was given at 0.3mg/kg/day and undetectable (<0.6 ng/ml) 5 days after weaning.Conclusions: Systemicadministration of a Kv1.3 blocker results in slight prolongation of graft survival after rat hind-limb allotransplantation while local administration into the skin has no effect under low dosetacrolimus therapy.

Disclosure: All authors have declared no conflicts of interest.